Choosing the investigation
The distribution of a species can be associated with environmental conditions. Relevant abiotic factors include light intensity, nutrient concentration and temperature. Biotic influences can include competition, predators and pathogens.
The investigation tests whether the distribution of a given species varies with a named environmental factor. For a plant species, either random frame quadrats or a systematic belt transect can be used depending on the habitat.
| Habitat | Sampling approach |
|---|---|
| No clear change in physical conditions across the area | Random quadrats are appropriate. |
| A clear environmental gradient is present | Systematic sampling along a belt transect is appropriate. |
For example, a transect investigating light intensity could extend from beneath a woodland canopy into an open area. An altitude survey could similarly investigate a change in temperature.
Apparatus
| Apparatus | Purpose |
|---|---|
| Quadrat | Measure percentage cover of the chosen plant species. |
| Tape measures | Construct a coordinate grid or establish a transect. |
| Digital thermometer | Measure soil temperature where this is the named factor. |
| Digital pH meter | Measure soil pH where this is the named factor. |
| Photometer | Measure light intensity where this is the named factor. |
| Random number generator | Select coordinates for random quadrat sampling. |